Brake Master cylinder:

Frederick

Frederick

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I did try to figure this out both here and thru internet searches but could not quite nail it down.
What is the difference between these two Master Cylinders? Aside from the numbers, why does one not have the screw to release the
innards?
0AB0DCC8-8746-4D74-9533-C79D1A21D613.JPG
 
I may be completely off on this, but I thought I remembered there being two different diameter internals? I remember ordering the wrong one for mine and having to reorder..Years ago, though...As far as getting into it, does one just have an internal snap ring around the shaft end?
 
I too recall the different diameter issue from replacing it in the early 80s. It looks like there were two different internal piston diameters depending on which brake booster is used? The "early style" booster shown here is what my 1972 Bavaria had (build date Feb 1972) which has a 22.2mm piston called out, and I recall seeing the larger "late style" booster on 1973 or later cars which shows a mc with 23.81mm spec'd.
 
Although e9, it is all right here regarding M/C and Booster.

E9 Changes: '69 to '74

Changes from 2800CS to 3.0CS for US/NA Market Mechanical and Engine Bay Changes Engine enlarged from 2.8L to 3.0L, US compression revised from 9.0:1 to 8.0:1, early 2800CS oil pan has no baffles and oil pressure switch is mounted at lower end of head vs. upper portion of head Water pump pulley...
e9coupe.com e9coupe.com
 
Those changes don't necessarily line up with the E3. My 02/1972 build Bavaria 3.0 had the "pancake" style booster, and I'm guessing the entire 1972 model year.
 
I was just posting which booster uses which M/C. Big booster changed at 3.0Si 3204544, 3.0SA 3152581, 3.0 Bav 3102474, 3.0 Bav A 3131124.
 
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